Apologies in advance for the slightly off topic post. This forum seemed the least inappropriate. Seeing the specifications for the G3 Atkinson Cycle Prius ICE it occurred to me that that engine might suit the Yaris in non-hybrid form, at least for the North American market. The specs are not so different from the current 1.5l Yaris ICE, in particular the peak torque (which after all is what really matters in everyday use) is very similar. Also, I doubt that the new ICE is much more expensive to produce, if indeed it is more expensive.
IIRC, Atkinson combustion engines have a very low torque at low RPM. In Hybrid engines, it's a good combination for an electric motor which has a very high torque at low RPM.
You may be correct. My understanding though is that they produce low torque for their size, and I'm talking about replacing the 1.5l Yaris ICE with a 1.8l Atkinson Cycle ICE. I would be surprised if the two torque curves were very different is shape.